Flame hardening of shafts



J. J. CROWE FLAME HARDENING OFSHAFTS March 3, 1942.

Filed May 22, 1936 z .INVENTOR,

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- ATTORNEY Patented Mar. 3, 194 2 FLAME HARDENING or SHAFTS John J. 'Crowe, Westfield, N. J., assignor to Air Reduction Company, Incorporated, New York, N. Y., a corporation of New York Application May 22,1936, Serial No. 81,239

8 Claims.

It is known to harden the surface of a shaft by the applicationof oxyacetylene or other flame of suflicient intensity, followed, in the direction of relative rotation, by the application of quenching fluid. A zone having been hardened in this manner, the heating and quenching agencies, or the shaft, may be displaced lengthwise, and thereupon .an adjoining zone may be hardened, these operations being repeated until the desired length of the shaft has been heat treated. Such an operation is discontinuous, and naturally results in leaving relatively soft strips between hardened areas.

In accordance with this invention the hardening of the surface of a shaft, either for its entire length, if that should be desired, or for any given part of its length, is effected continuously and in a practical manner, by producing relative rotary and longitudinal motion simultaneously, and causing the quenching, when quenching is employed, to follow the heating in the direction of longitudinal motion instead of in the direction of rotary motion, th speeds of rotary and longitudinal motions being so coordinated that the shaft is heated to ,a proper depth completely around the shaft and quenched without leaving any soft areas. An additional advantage of this method is that greater depth of hardening can be obtained without overheating the surface.

In certain instances quenching may be omitted. Some steel compositions will take on the desired degree of hardness as the result merely of being heated above the critical range and then being allowed to cool in air. In other cases the mass of steel underlying the heated metal may conduct the heat away sufficiently rapidly to give the necessary hardness.

In the accompanying drawing, forming part hereof:

1 is a cross-section through a rotatin shaft in process of being treated by the application of flames and quenching jets, the heating torch being shown in fragmentary end elevation;

Fig. 2 is a side elevation of the shaft and heating and cooling agencies;

Fig. 3 is a view similar to Fig. 1 showing a shaft being acted upon by a plurality of torches and sets of water jets; and

Fig. 4 is a side view corresponding to Fig. 3, the torch and water nozzles in front, together with the flame jets and cooling jets being indicated schematically,

The same reference characters designate similar things in all of the views.

The heating device 2 is preferably a multiple jet oxyacetylene torch designed to deliver a flame or a system of flames which may be of substantial width lengthwise of the shaft 3. Flame jets are shown at F and water jets at W, W, the jets W being the quenching jets.

The arrow in Fig. 1 indicates rotation of the shaft, and that of Fig, 2 indicates motion of the torch lengthwise of the shaft. Thes continuous motions may be produced in any desired manner,

even by causing the torch to move in a-helical path about a stationary shaft.

The water jets may be delivered through the torch block, or through separate pieces 4, 4*-

as shown. These need not be at the ends of the torch block, but may be anywhere around the shaft, provided the quenching action of the jets W follows the heating action in the direction of longitudinal motion, and that the jetsW', if employed, precede the heating in the same direction. The use of the cooling jets W is optional.

If the shaft is rotated relatively rapidly, for example at a speed of the order of 10 to R. P. M., and the torch is advanced in the direction of Fig. 2 at a rate which is quite slow and much less than the effective tip width per revolution, a very uniform hardening is obtained over the entire circumference and throughout the length of the shaft that is to be treated. The speeds of revolution and translation may bevaried widely provided a speed of longitudinal motion, beyond which soft or insufiiciently hardened strips would be left, is not exceeded. The proper speed of longitudinal motion is relative and depends upon the size of shaft and the extent of the heating system lengthwise and circumferentially of the shaft, but can be readily ascertained from these instructions, for any particular case. I v

If the torch is advanced at uniform speed, and if the water jets W are notemployed, there is an accumulation of heat ahead of the torch, which tends to cause the depth of hardening to be non-uniform along the length of the shaft. This difliculty can be overcome in either of two ways. One way is gradually to increase the speed of travel of the torch to a maximum at which heat accumulation ahead of the torch ceases, thereafter holding the speed constant. The other way is to use cooling jets W in advance of the hardened zone.

At the commencement of the operation it is advisable to hold'the torch stationary and to revolve the shaft until a zone comes to the necessary heat, whereupon the heating and cooling agencies are put in longitudinal motion;

If heating flames are applied at two or more regions about the circumference of the shaft, or if the flame system or systems are otherwise extended circumferentially, the rate of longitudinal motion may be increased for a given width of the system along the shaft; on the other hand, the width of the system may be decreased, ultimately to flame jets in single row simultaneously putting heat into the shaft around much of the circumference.

Figs. 3 and 4 illustrate the hardening of a shaft with three torches and sets of water nozzles disposed in a circumferential zone, thus extending the input of heat about the shaft. The width of each flame system may, if desired, be contracted as compared with Figs. 1 and 2.

While water has been spoken of as the quenching and pre-cooling fluid, it will be understood that air, nitrogen or any other fluid suitable for quenching or cooling may be employed, and as previously stated certain shafts may be hardened by heating in the manner herein described, without the quenching.

I claim:

1. The nethod of hardening shafts and other round stock involving the application of flame heat to the surface of the round stock followed by quenching, characterized in that a plurality of flame jets, at least some of which are spaced between the heating agency and the round stock, that the speed of longitudinal motion is kept slow in relation to the speed of rotation, and that the circumferential extent of the flame heat is correlated with the rate of longitudinal heating to control the penetration of the heat.

5. The method of hardening shafts and other round stock involving the application of flame heat to the surface of the round stock, charac terized in that continuous relative rotary and unidirectional longitudinal motions are produced between the heating agency and the roum stock, that the speed of longitudinal motion is kept slow in relation to the speed of rotation, and further characterized in that the speed of longitudinal motion is gradually increased during the time that heat accumulates in the stock ahead of the torch and in a manner to compensate for such accumulation of heat.

6. The method of hardening shafts and other round stock involving the application of flame heat to the surface of the round stock, characterized in that continuous relative rotary and longitudinally along the shaft, are applied to the 130 surface of the shaft over an angular extent of the surface which is correlated with the longitudinal extent of the flame system so as to obtain the desired penetration of the heat prior to hardening, continuous relative rotary and longitudinal motions are produced between the flame system and the surface of the round stock, and the quenching is simultaneous with the heating and follows closebehind the region of heating in the direction of longitudinal motion.

2. The method of hardening shafts and other round stock involving the application of flame heat to the surface of the round stock followed by quenching, characterized in that continuous relative rotary and longitudinal motions are produced between the heating agency and the round stock, that the quenching is simultaneous with the heating and follows close behind the region of heating in the direction of longitudinal motion, that the speed of longitudinal motion is kept slow in relation to the speed of rotation, and that the application of heat is confined to a limited angle of the shaft surface, which angle is so related to the rate of longitudinal motion that a substantial penetration of the heat below the surface of the shaft is obtained before the shaft is quenched.

3. The method of hardening shafts and other round stock involving the application of flame heat to the surface of the round stock, characterized in that continuous relative rotary and unidirectional longitudinal motions are produced between the heating agency and the round stock to heat the stock progressively along its length, and that the flame heat is applied at each instant over a total area extending for a substantial gas distance longitudinally along the shaft but for unidirectional longitudinal motions are produced between the heating agency and the round stock, that the speed of longitudinal motion is kept slow in relation to the speed of rotation, and further characterized in that the speed of longitudinal motion is gradually increased up to a definite maximum during the time that heat is accumulating in the stock ahead of the torch, and the speed of longitudinal motion is held constant for the part of the heating operation during which the metal immediately ahead of the torch is at substantially constant temperature.

7. The method of hardening shafts and other round stock as set forth in claim 4, further characterized in that cooling fluid is directed against the surface of the round stock in front of the longitudinal advance of the heating agency.

8 The method of hardening a cylindrical work-piece by applying a system of heating flames to an area of the cylindrical surface while rotating said work-piece about its axis and producing relative longitudinal movement of the flame system and the work-piece, which method is characterized by rotation of the piece at a peripheral speed faster than the relative longitudinant movement of the flame system, the difference in speed being such that said flame system advances substantially less than its longitudinal extent during each revolution of the workpiece, controlling the depth of hardening by applying the flame system to an area of the surface the length of which area is so related to the speed of said longitudinal movement that during the time required for the full length of the flame system to pass any given section of the workpiece, said work-piece is heated above the critical temperature for the depth to which hardening is desired, correlating the peripheral extent of the heating system with its longitudinal extent by limiting the peripheral extent to such an angle that each point on the face of the work-piece is under the flame system for only a part of the heating period and is heated during said period to a temperature less than the fusing point of the metal, and hardening the work-piece progressively along its length by applying a quenching jet to the cylindrical surface simultaneously with the heating of said surface but at some distance longitudinally behind the flame system.

JOHN J. CROWE. 

